1. Field of the Invention
The present invention relates to a liquid crystal driver and a liquid crystal driving method in which same image signal is supplied to a liquid crystal panel in a unit interval with an even number of fields composed of a positive field and a negative field, and to a liquid crystal display device employing the liquid crystal driver and the liquid crystal driving method, with which picture quality is improved at the time of displaying a moving picture.
2. Description of the Related Art
In recent years, an active matrix liquid crystal panel has been improved to have high resolution and high luminance, and as a result, the liquid crystal panel is used not only as a display device for a personal computer and a portable information terminal (such as a mobile phone unit) but also as a display device for a television receiver which is primarily intended to display a moving picture. In addition, personal computers and portable information terminals have recently been used for receiving and displaying moving picture contents.
In an active matrix liquid crystal panel, a liquid crystal material is sealed between a drive substrate (silicon substrate, for example) in which a pixel electrode is formed and a glass substrate in which a transparent common electrode is formed. Since light transmittance of a liquid crystal material changes in response to a potential difference between the pixel electrode and the common electrode by writing an image signal to the pixel electrode (applying voltage corresponding to the luminance of the image signal), the incident light is modulated so that an image is displayed.
In a liquid crystal panel, image deterioration such as a residual image due to slow response speed (slow response in the change of the light transmittance of the liquid crystal material) may occur at the time of displaying a moving picture that moves fast (in which luminance fluctuates greatly). In Japanese Unexamined Patent Application Publication No. 2002-189458 (JP 2002-189458 A), there is proposed that time to reach a desired luminance is shortened by using a characteristic that the larger the change in drive voltage becomes, the faster the response speed of a liquid crystal panel becomes. JP 2002-189458 A proposes that a difference between the luminance of an image signal of one frame before and the luminance of the image signal of the present frame is obtained and a correction amount of luminance corresponding to the difference is added to and subtracted from the luminance of the image signal of the present frame so that the corrected image signal is supplied to the liquid crystal panel.